The present invention generally relates to a laminated structure. More specifically, the present invention relates to a laminated structure suitable as a reflective electrode, a reflective film, a wiring or the like, its manufacturing method, a display device, and a display unit that employ same.
In recent years, as one of the flat panel displays, an organic light-emitting display which uses organic light-emitting devices has been noted. The organic light-emitting display has characteristics that its viewing angle is wide and its power consumption is low since it is a self-luminous type display. The organic light-emitting display is also thought of as a display having sufficient response to high-definition and high-speed video signals, and is under development toward the practical use.
As an organic light-emitting device, for example, a laminate wherein a first electrode, an organic layer including a light-emitting layer, and a second electrode are sequentially layered on a substrate with a TFT (Thin Film Transistor), a planarizing layer and the like in between is known. Light generated in the light-emitting layer may be extracted from the substrate side in some cases, and may be extracted from the second electrode side in other cases.
As an electrode on the side where light is extracted, a transparent electrode made of a conductive material having transparency such as a compound containing indium (In), tin (Sn), and oxygen (O) (ITO: Indium Tin Oxide) is often used. Conventionally, various structures of the transparent electrode have been proposed. For example, in order to avoid cost rise due to a thick film of ITO, a transparent electrode wherein a metal thin film made of silver (Ag) or the like and a high refractive index thin film made of zinc oxide (ZnO) are layered has been proposed (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-234792). In the transparent electrode, a thickness of the high refractive index thin film is set to from 5 nm to 350 nm, and a thickness of the metal thin film is set to from 1 nm to 50 nm. In this regard, the thickness of the high refractive index thin film is relatively thicker than the thickness of the metal thin film to raise the transparency. In addition, reflection on the surface of the metal thin film is reduced by the high refractive index thin film.
Various metal electrodes are often used for the electrode on the side where light is not extracted. For example, when light is extracted from the second electrode side, the first electrode as an anode is made of, for example, a metal such as chromium (Cr). Conventionally, for example, there is a suggestion that the first electrode is constructed as a two-layer structure including a metal material layer made of chromium and a buffer thin film layer made of an oxide including chromium, and surface roughness of chromium making the metal material layer is reduced by the buffer thin film layer (for example, refer to Japanese Unexamined Patent Application Publication No. 2002-216976).
When light is extracted from the second electrode side, light generated in the light-emitting layer is directly extracted through the second electrode in some cases, but light generated in the light-emitting layer is once reflected by the first electrode and is emitted through the second electrode in other cases. Conventionally, the first electrode has been made of chromium or the like. Therefore, there has been a problem that light absorbance in the first electrode is large and loss of light extracted after reflected by the first electrode is large. The light absorbance in the first electrode has a significant impact on the organic light-emitting devices. When light-emitting efficiency is low, a current necessary to obtain the same intensity is increased. An increase of the driving current significantly affects device life, which is very important for practical use of the organic light-emitting devices.
Therefore, it can be thought that the first electrode is made of silver (Ag) which has the highest reflectance among metals or an alloy containing silver. In this case, since silver is very reactive, in order to prevent its deterioration or corrosion, providing a buffer thin film layer or the like on a surface of the silver layer as in the foregoing conventional art is considered to be useful.
However, when the first electrode has a laminated structure wherein the buffer thin film layer is provided on the surface of the silver layer, there is a risk that a favorable patterning of the first electrode becomes difficult if using the wet etching technique which is conventionally used for patterning silver. The reason thereof is that there is a difference between etching rates of the silver layer and the buffer thin film layer, so that only etching in the silver layer may rapidly proceed. When a shape of the first electrode is not good, an insulating film covering side surfaces of the first electrode is subject to deposition failure or holes, leading to causing defect of the organic light-emitting devices. Dry etching technique for silver has not been developed yet.